Before removing the redundant shapelets, we firstly need to get the shapelets candidates set. The original shapelets extraction algoritm is time consuming and complexity is \( O({n^2}{m^4}) \) , \(n\)  is the number of time series in the data set, \(m\)  is the length of each time series. In order to improve the efficiency of shapelets based classification method, we follow the method proposed in [1]}, which transformed the data sets through SAX method and decreased the time complexity to \( O(n{m^2}) \) .
